var keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
//将Ansi编码的字符串进行Base64编码
function base64_encode(input) {
  var output = "";
  var chr1, chr2, chr3 = "";
  var enc1, enc2, enc3, enc4 = "";
  var i = 0;

  do {
	chr1 = input.charCodeAt(i++);
	chr2 = input.charCodeAt(i++);
	chr3 = input.charCodeAt(i++);

	enc1 = chr1 >> 2;
	enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
	enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
	enc4 = chr3 & 63;

	 if (isNaN(chr2)) {
		enc3 = enc4 = 64;
	 } else if (isNaN(chr3)) {
		enc4 = 64;
	 }

	 output = output + 
		keyStr.charAt(enc1) + 
		keyStr.charAt(enc2) + 
		keyStr.charAt(enc3) + 
		keyStr.charAt(enc4);
	 chr1 = chr2 = chr3 = "";
	 enc1 = enc2 = enc3 = enc4 = "";
  } while (i < input.length);

  return output;
}

//将Base64编码字符串转换成Ansi编码的字符串
function base64_decode(input) {
	var output = "";
	var chr1, chr2, chr3 = "";
	var enc1, enc2, enc3, enc4 = "";
	var i = 0;
	//if(typeof input.length=='undefined')return '';
	if(input.length%4!=0){
		return "";
	}
	var base64test = /[^A-Za-z0-9\+\/\=]/g;
	
	if(base64test.exec(input)){
		return "";
	}
	
	do {
		enc1 = keyStr.indexOf(input.charAt(i++));
		enc2 = keyStr.indexOf(input.charAt(i++));
		enc3 = keyStr.indexOf(input.charAt(i++));
		enc4 = keyStr.indexOf(input.charAt(i++));
		
		chr1 = (enc1 << 2) | (enc2 >> 4);
		chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
		chr3 = ((enc3 & 3) << 6) | enc4;
		
		output = output + String.fromCharCode(chr1);
		
		if (enc3 != 64) {
			output+=String.fromCharCode(chr2);
		}
		if (enc4 != 64) {
			output+=String.fromCharCode(chr3);
		}
		
		chr1 = chr2 = chr3 = "";
		enc1 = enc2 = enc3 = enc4 = "";
	
	} while (i < input.length);
	return output;
}
